Revitalizing Old Field Devices Through Ethernet Encapsulation

Let’s face it—we live in a world that is dominated by radio waves and twisted pairs of copper. Our homes, our communities, and the places we work are all connected in one way or another. The information we need and want is always at our fingertips. That’s where it belongs, and that’s where we expect it to be.

For industrial organizations, that raises the question of what is to be done with all those field devices that seem to have missed the on-ramp to the information superhighway. We could update our control systems, but what if we are really looking for a simple, low-cost, low-impact solution that gives us all the connectivity we need? One viable solution for manufacturing leaders to consider is Ethernet encapsulation.

What is Ethernet encapsulation?

Before we take a deeper dive in, let’s begin with a quick look at what Ethernet encapsulation is and how the process itself works, as well as why it is important for connectivity in general and industrial connectivity in particular.

Ethernet encapsulation is a process that allows data to be sent over Ethernet networks. It may be counterintuitive, but data can’t be sent on a continuous basis. Instead, data is broken into pieces—or “packets.” However, those packets need to incorporate information about how the data should be handled as it makes its way through different connection nodes and layers of Ethernet networks. The process of encapsulation puts an envelope (i.e., header and trailer) around each data payload. The header and trailer embed control data into the data itself and gives each point it comes into contact with information on what should be done with the data. This control data is required for messages that wish to be sent and routed over Ethernet networks.

What is the Ethernet encapsulation process?

There are a couple of different encapsulation processes to choose from, but let’s take a deeper dive into one as a way to see the process in action. The Open Systems Interconnection (OSI) model separates system layers by function, and each layer has a specific set of functions. Understanding how OSI works provides a stronger understanding into how the overall process works and why it’s important to enterprise connectivity and communication.

During the encapsulation process, a source computer will take a data packet from the application layer and send it toward the physical layer. When the data package hits Layer 4, which is also called the transport layer, data encapsulation begins. Each layer adds the appropriate data to the packet and ensures that it travels through the system to its destination.

Let’s take a quick look at the layers and the role that each play in the encapsulation process:

1. The lowest layer is the physical layer, which adds the bits that mark a packet’s header and trailer.
2. From there, the packet progresses to the data link layer, which oversees the interaction between sending and receiving systems. At this juncture, destination details are added to the header.
3. After passing through the data link layer, the packet continues on to the network layer, where the internet address information is added.
4. From there, the data travels to the transport layer, where the encapsulation begins. At this phase, a transport protocol, such as TCP, ensures that the packet will reach its destination and adds a byte count to indicate size to a header.
5. Next is the session layer, which adds information about how the data is going to flow throughout the system.
6. At the next layer, also called the presentation layer, data is put into a form that can be used by an application.
7. The application layer directly interacts with the computer, where the data is accessed by an application and used.

This detailed protocol also happens in reverse—a process known as decapsulation. Once decapsulation removes the header and trailer data, a device can access the original data.

What are the types of Ethernet encapsulation?

Those who are learning about the encapsulation process for the first time may wonder what types of encapsulation are critical to understand. Essentially, there are two types of Ethernet framing that can be used:

• The first is the IEEE 802.3 Ethernet standard, which has been evolving for several years to meet the needs of emerging technologies. It was first introduced in 1983 by IEEE as a move to help standardize communication protocols between different manufacturers and developers, for greater interoperability and to simplify development.
• Ethernet II (formerly called the DIX Standard) is the second version.

The differences between the two types of encapsulation frames are minimal. The differences are primarily found in the headers of their respective packets. One of the most important differences has to do with length: If the data byte length exceeds 1500, it must be supported by an Ethernet II frame. If the length is less than 1500, the frame is IEEE 802.3.

However, both IEEE 802.3 and Ethernet II can play an important role in implementing ethernet encapsulation. Industrial communications efforts may incorporate one or both frames, depending on the ultimate goals, age of legacy equipment, and other factors.

What are examples of Ethernet encapsulation?

Let’s take a look at one of the most common forms of Ethernet encapsulation in an industrial setting. The demand for automation and industrial connectivity has raised the importance of these types of communication protocols, and finding ways to utilize this standardized approach can open up significant opportunities for streamlining and optimization. 

A common use-case for Ethernet encapsulation in industrial settings is integrating a Serial-connected Programmable Logic Controller (PLC) to an Ethernet network for the purpose of programming, control, and data acquisition without the need to utilize short-run Serial cabling and add-on Serial cards or dongles for host PCs. With Ethernet encapsulation, the Serial-connected PLC can become a part of the centrally-managed Ethernet network, allowing for most all of the benefits of Ethernet – modern security features like message encryption, communications at a distance, managed bandwidth and data flow, and packet dissection and inspection – without forcing users to replace the PLC itself that might be entirely sufficient save for its networking interface.

In particular, adopting this standard form of communication and sharing data can help improve data speeds, enhance security, and implement device integrations such as IIoT. Software vendors know that when Ethernet encapsulation is used, they’ll have access to contextual data that can be incorporated into how the connected software processes the information that sensors collect. Rich data and rich metadata offer the opportunity for better control, data sharing, and laying the technical foundation for automation by transmitting essential data as part of the natural flow of information.

Can PTC’s Kepware help with Ethernet encapsulation?

Ethernet encapsulation is certainly not new to Kepware, but it does bring new life to devices with limited or legacy networking options. Fortunately, the Ethernet encapsulation is a built-in feature available with most of Kepware’s Serial OPC protocol drivers. All that’s needed is a low-cost piece of hardware known as a serial-to-Ethernet converter (also known as a terminal or serial server). 

The converter is placed within the recommended RS-232/422/485 cabling distance and then connected to the local area network via Ethernet. Once configured properly (usually through a web interface), it can be accessed by Kepware at a distance only limited by the network’s infrastructure. And there you have it—information from that old field device is now at your fingertips.

Kepware recommends using converters that support “raw socket connections”, also termed “TCP server” or “socket servers”. This eliminates the need for additional Serial COM port virtualization software and provides far more flexibility than the standard protocols that are offered with some “smart” serial-to-Ethernet converters. The raw socket configuration also mitigates timing errors and allows Kepware to communicate with the field device in the exact manner it would expect from a direct serial connection.

It’s time to bring new life to that old field device and give this feature a try.

Conclusion 

Ethernet encapsulation is a critical tool that enables data to be packaged and safely transmitted across Ethernet networks. Embracing this approach to sharing information within a connected industrial environment helps organizations gain better control of their data. While encapsulation isn’t new, the potential of using this process to power Ethernet on the factory floor or in an industrial setting can help you introduce automation, enterprise connectivity, and an effective IIoT solution to support the needs of Industry 4.0.

Ready to learn more about encapsulation and how it can play a role in your industrial connectivity efforts? Contact PTC today to speak with a connectivity specialist.